The TBRU will operate a Clinical Core directed by Dr. Horsburgh of the Boston University School of Public Health. The Clinical Core will take overall responsibility of all human studies in the proposed TBRU protocols and will work closely with the Regulatory Coordinator and Data Management Center (DMC) in the Administrative Core to coordinate approved protocols and unit-wide scientific activities in concert with scientific decisions of the TBRU. The TBRU Clinical Core will oversee the development and implementation of the clinical projects, including protocol development, regulatory approvals, data management, and site monitoring. The human studies will be conducted at the NiJcleo de Doencas Infecciosas (NDI) in Vitoria, Brazil led by Dr. Reynaldo Dietze, and the National Medical Center (NMC) in Seoul, Republic of Korea (ROK) led by Dr. Ray Cho. Dr. Horsburgh will work closely with Drs. Dietze and Cho to ensure timely completion of all project milestones. The Clinical Core will coordinate with the existing NIAID intramural team in the ROK, and the established ICIDR study team in Brazil when the TBRU projects begin. There are parallels in the studies to be conducted in South Korea and Brazil. In Project 1, prospective observational cohort studies of household contacts of multidrug resistant (MDR)-PTB (Korea) and of drug-susceptible (DS) -PTB (Brazil) will be conducted. The endpoint will be incident TB. In Project 3, a prospective observational cohort study of MDR-TB cases (Korea) and DS-PTB cases (Brazil) beginning at the end of treatment will be conducted, the endpoint being relapse. In both projects, samples will be collected and stored, and then accessed when a subject reaches a study endpoint along with samples from suitable controls. There is considerable overlap as well in the approaches to biomarker discovery.